The JAK1/2 inhibitor ruxolitinib downregulates the immune checkpoint protein B7H3 in multiple myeloma.

We hypothesized that ruxolitinib may inhibit the immune checkpoint protein, B7H3; and, thus, investigated its effects on this immune inhibitor using multiple myeloma (MM) cell lines, bone marrow (BM) mononuclear cells from MM patients and human MM LAGλ -1A xenografts. Ruxolitinib reduced B7H3 gene and protein expression and increased IL-2 and CD8 gene expression. These results suggest that ruxolitinib inhibition of B7H3 may restore exhausted T-cell activity in the MM BM tumor microenvironment.

Multiscale profiling of protease activity in cancer.

Diverse processes in cancer are mediated by enzymes, which most proximally exert their function through their activity. High-fidelity methods to profile enzyme activity are therefore critical to understanding and targeting the pathological roles of enzymes in cancer. Here, we present an integrated set of methods for measuring specific protease activities across scales, and deploy these methods to study treatment response in an autochthonous model of Alk-mutant lung cancer. We leverage multiplexed nanosensors and machine learning to analyze in vivo protease activity dynamics in lung cancer, identifying significant dysregulation that includes enhanced cleavage of a peptide, S1, which rapidly returns to healthy levels with targeted therapy. Through direct on-tissue localization of protease activity, we pinpoint S1 cleavage to the tumor vasculature. To link protease activity to cellular function, we design a high-throughput method to isolate and characterize proteolytically active cells, uncovering a pro-angiogenic phenotype in S1-cleaving cells. These methods provide a framework for functional, multiscale characterization of protease dysregulation in cancer.

Protease Activity Analysis: A Toolkit for Analyzing Enzyme Activity Data.

Analyzing the activity of proteases and their substrates is critical to defining the biological functions of these enzymes and to designing new diagnostics and therapeutics that target protease dysregulation in disease. While a wide range of databases and algorithms have been created to better predict protease cleavage sites, there is a dearth of computational tools to automate analysis of in vitro and in vivo protease assays. This necessitates individual researchers to develop their own analytical pipelines, resulting in a lack of standardization across the field. To facilitate protease research, here we present Protease Activity Analysis (PAA), a toolkit for the preprocessing, visualization, machine learning analysis, and querying of protease activity data sets. PAA leverages a Python-based object-oriented implementation that provides a modular framework for streamlined analysis across three major components. First, PAA provides a facile framework to query data sets of synthetic peptide substrates and their cleavage susceptibilities across a diverse set of proteases. To complement the database functionality, PAA also includes tools for the automated analysis and visualization of user-input enzyme-substrate activity measurements generated through in vitro screens against synthetic peptide substrates. Finally, PAA supports a set of modular machine learning functions to analyze in vivo protease activity signatures that are generated by activity-based sensors. Overall, PAA offers the protease community a breadth of computational tools to streamline research, taking a step toward standardizing data analysis across the field and in chemical biology and biochemistry at large.

Aging and matrix viscoelasticity affect multiscale tendon properties and tendon derived cell behavior.

Aging is the largest risk factor for Achilles tendon associated disorders and rupture. Although Achilles tendon macroscale elastic properties are suggested to decline with aging, less is known about the effect of maturity and aging on multiscale viscoelastic properties and their effect on tendon cell behavior. Here, we show dose dependent changes in native multiscale tendon mechanical and structural properties and uncover several nanoindentation properties predicted by tensile mechanics and echogenicity. Alginate hydrogel systems designed to mimic juvenile tendon microscale mechanics revealed that stiffness and viscoelasticity affected Achilles tendon cell aspect ratio and proliferation during aging. This knowledge provides further evidence for the negative impact of maturity and aging on tendon and begins to elucidate how viscoelasticity can control tendon derived cell morphology and expansion. STATEMENT OF SIGNIFICANCE: Aging is the largest risk factor for Achilles tendon associated disorders and rupture. Although Achilles tendon macroscale elastic properties are suggested to decline with aging, less is known about the effect of maturity and aging on multiscale viscoelastic properties and their effect on tendon cell behavior. Here, we show dose dependent changes in native multiscale tendon mechanical and structural properties and uncover several nanoindentation properties predicted by tensile mechanics and echogenicity. Alginate hydrogel systems designed to mimic juvenile tendon microscale mechanics revealed that stiffness and viscoelasticity affected Achilles tendon cell spreading and proliferation during aging. This knowledge provides further evidence for the negative impact of maturity and aging on tendon and begins to elucidate how viscoelasticity can control tendon derived cell morphology and expansion.

Ruxolitinib reverses checkpoint inhibition by reducing programmed cell death ligand-1 (PD-L1) expression and increases anti-tumour effects of T cells in multiple myeloma.

Multiple myeloma (MM) tumour cells evade host immunity through a variety of mechanisms, which may potentially include the programmed cell death ligand-1 (PD-L1):programmed cell death protein-1 (PD-1) axis. This interaction contributes to the immunosuppressive bone marrow (BM) microenvironment, ultimately leading to reduced effector cell function. PD-L1 is overexpressed in MMBM and is associated with the resistance to immune-based approaches for treating MM. Ruxolitinib (RUX), an inhibitor of the Janus kinase (JAK) family of protein tyrosine kinases, is approved for myeloproliferative diseases. We investigated the effects of RUX alone or in combination with anti-MM agents on the expression of PD-L1 and T-cell cytotoxicity in MM. We showed that the expression of the PD-L1 gene was markedly increased in BM mononuclear cells from patients with MM with progressive disease versus those in complete remission. Furthermore, RUX treatment resulted in a concentration-dependent reduction of PD-L1 gene expression in the MM tumour cells cultured alone or co-cultured with stromal cells compared with untreated cells. The results also demonstrated that RUX increased MM cell apoptosis in the presence of interleukin-2-stimulated T cells to a similar degree as the treatment with anti-PD-1 or anti-PD-L1 antibodies. In summary, these results indicate that RUX can block PD-L1 expression resulting in augmentation of anti-MM effects of T cells.

JAK1/2 pathway inhibition suppresses M2 polarization and overcomes resistance of myeloma to lenalidomide by reducing TRIB1, MUC1, CD44, CXCL12, and CXCR4 expression.

Monocytes polarize into pro-inflammatory macrophage-1 (M1) or alternative macrophage-2 (M2) states with distinct phenotypes and physiological functions. M2 cells promote tumour growth and metastasis whereas M1 macrophages show anti-tumour effects. We found that M2 cells were increased whereas M1 cells were decreased in bone marrow (BM) from multiple myeloma (MM) patients with progressive disease (PD) compared to those in complete remission (CR). Gene expression of Tribbles homolog 1 (TRIB1) protein kinase, an inducer of M2 polarization, was increased in BM from MM patients with PD compared to those in CR. Ruxolitinib (RUX) is an inhibitor of the Janus kinase family of protein tyrosine kinases (JAKs) and is effective for treating patients with myeloproliferative disorders. RUX markedly reduces both M2 polarization and TRIB1 gene expression in MM both in vitro and in vivo in human MM xenografts in severe combined immunodeficient mice. RUX also downregulates the expression of CXCL12, CXCR4, MUC1, and CD44 in MM cells and monocytes co-cultured with MM tumour cells; overexpression of these genes is associated with resistance of MM cells to the immunomodulatory agent lenalidomide. These results provide the rationale for evaluation of JAK inhibitors, including MM BM in combination with lenalidomide, for the treatment of MM patients.

Serum B-cell maturation antigen (BCMA) reduces binding of anti-BCMA antibody to multiple myeloma cells.

B-cell maturation antigen (BCMA), a tumor necrosis factor receptor (TNFR) family member, is selectively expressed on terminally differentiated B-lymphocytes including multiple myeloma (MM) tumor cells. We sought to determine whether circulating (c)BCMA in MM serum interferes with antiBCMA antibody binding to MM cells. An enzyme-linked immunosorbent assay (ELISA) was used to determine serum (s) BCMA levels among 379 samples from patients with relapsed/refractory MM (RRMM). Furthermore, flow cytometric and immunofluorescent studies were used to examine if concentrations of BCMA in patients' serum were high enough to interfere with the binding of anti-BCMA antibody to MM tumor cells. We have shown that BCMA is elevated in the serum from MM patients and that the median concentration of sBCMA from RRMM patients was 176 ng/mL (n = 379). Additionally, there was a consistent decrease in the binding of anti-BCMA antibody to MM tumor cells with sBCMA level ≥156 ng/mL. Together, these results demonstrate that circulating BCMA levels in most RRMM patients are high enough to interfere with anti-BCMA antibody binding to MM tumor cells and may interfere with BCMA-targeted immune-based therapies.

The clinical significance of B-cell maturation antigen as a therapeutic target and biomarker.

INTRODUCTION: B-cell maturation antigen (BCMA) is a cell membrane bound tumor necrosis factor receptor family member that is expressed exclusively on late stage normal and malignant B-cells and plasma cells. Addition of two of its ligands, B-cell activating factor and a proliferation inducting ligand, to normal B-cells cause B-cell proliferation and antibody production. Serum BCMA is elevated among patients with multiple myeloma (MM) and chronic lymphocytic leukemia (CLL), and is a prognostic and monitoring tool for these patients. The first anti-BCMA antibody (Ab) was developed in 2007. Recently, biotech and pharmaceutical companies have created various forms of BCMA-directed Abs (naked Abs, Ab drug conjugates, and bispecific Abs) and cellular therapies (chimeric antigen receptor T-cells) with promising clinical results. Areas covered: This BCMA review encompasses full-text publications of original research articles and abstracts presented at hematology/oncology meetings. Expert commentary: The limited preclinical and ongoing clinical studies published to date evaluating BCMA-directed therapies have shown great promise. It has also been demonstrated that BCMA is solubilized and elevated in the blood of MM, Waldenstrom's macroglobulinemia and CLL patients, and is also responsible for the immune deficiency in MM. Reducing circulating levels may improve the efficacy of these treatments.

The Role of B-Cell Maturation Antigen in the Biology and Management of, and as a Potential Therapeutic Target in, Multiple Myeloma.

B-cell maturation antigen (BCMA) was originally identified as a cell membrane receptor, expressed exclusively on late stage B-cells and plasma cells (PCs). Investigations of BCMA as a target for therapeutic intervention in multiple myeloma (MM) were initiated in 2007, using cSG1 as a naked antibody (Ab) as well as an Ab-drug conjugate (ADC) targeting BCMA, ultimately leading to ongoing clinical studies for previously treated MM patients. Since then, multiple companies have developed anti-BCMA-directed ADCs. Additionally, there are now three bispecific antibodies in development, which bind to both BCMA and CD3ε on T-cells. This latter binding results in T-cell recruitment and activation, causing target cell lysis. More recently, T-cells have been genetically engineered to recognize BCMA-expressing cells and, in 2013, the first report of anti-BCMA-chimeric antigen receptor T-cells showed that these killed MM cell lines and human MM xenografts in mice. BCMA is also solubilized in the blood (soluble BCMA [sBCMA]) and MM patients with progressive disease have significantly higher sBCMA levels than those responding to treatment. sBCMA circulating in the blood may limit the efficacy of these anti-BCMA-directed therapies. When sBCMA binds to B-cell activating factor (BAFF), BAFF is unable to perform its major biological function of inducing B-cell proliferation and differentiation into Ab-secreting PC. However, the use of γ-secretase inhibitors, which prevent shedding of BCMA from PCs, may improve the efficacy of these BCMA-directed therapies.

Anti-angiogenic and anti-multiple myeloma effects of oprozomib (OPZ) alone and in combination with pomalidomide (Pom) and/or dexamethasone (Dex).

Oprozomib (OPZ or ONYX 0912) is an irreversible, orally administered proteasome inhibitor (PI) and an analog of carfilzomib. We set out to determine the anti-angiogenic effect of OPZ using the choriollantoic membrane/feather bud (CAM/FB) model and its anti-MM effects using MM xenograft models (LAGκ-1A, LAGλ-1). OPZ significantly reduced blood vessel formation, endothelial gene and protein expression using the CAM/FB assay. In vivo, we determined the anti-MM effects of OPZ, dexamethasone (Dex) and pomalidomide (Pom) and showed that the combinations of two drugs (OPZ+Dex or OPZ+Pom) showed marked anti-MM effects when compared to monotherapy. Pom+Dex and the triplicate combination (OPZ+Pom+Dex) showed more anti-MM effects when compared to the doublets of either OPZ+Dex or OPZ+Pom; continued treatment with all three drugs (OPZ+Pom+Dex) was superior when compared to Pom+Dex, in both MM xenograft models tested. These studies show that OPZ has anti-angiogenic effects, and that the combination of OPZ, Dex and Pom produces greater anti-MM effects in vivo when compared to any of the doublet combinations. These studies provide further support for clinical trials evaluating OPZ in combination with Pom and Dex.

Combined TRAF6 Targeting and Proteasome Blockade Has Anti-myeloma and Anti-Bone Resorptive Effects.

TNF receptor-associated factor 6 (TRAF6) has been implicated in polyubiquitin-mediated IL1R/TLR signaling through activation of IκB kinase (IKK) to regulate the NF-κB and JNK signaling pathways. Here, TRAF6 protein was determined to be overexpressed in bone marrow mononuclear cells (BMMC) from patients with multiple myeloma. TRAF6 expression in BMMCs from patients with progressive disease is significantly elevated as compared with individuals in complete remission, with monoclonal gammopathy of undetermined significance, or healthy subjects. Furthermore, TRAF6 dominant-negative (TRAF6dn) peptides were constructed which specifically reduced TRAF6 signaling and activation of IKK. TRAF6 not only reduced cellular growth but also increased the apoptosis of multiple myeloma tumor cells in a concentration-dependent fashion. Because TRAF6 activates IKK through polyubiquitination, independent of its proteasome activity, a TRAF6dn peptide was combined with the proteasome inhibitors bortezomib or carfilzomib to treat multiple myeloma. Importantly, targeting of TRAF6 in the presence of proteasome inhibition enhanced anti-multiple myeloma effects and also decreased TLR/TRAF6/NF-κB-related signaling. Finally, TRAF6dn dose dependently inhibited osteoclast cell formation from CD14+ monocytes, induced with RANKL and mCSF, and markedly reduced bone resorption in dentin pits. In all, these data demonstrate that blocking TRAF6 signaling has anti-multiple myeloma effects and reduces bone loss.Implications: The ability to target TRAF6 signaling and associated pathways in multiple myeloma suggests a promising new therapeutic approach. Mol Cancer Res; 15(5); 598-609. ©2017 AACR.

Serum B-cell maturation antigen: a novel biomarker to predict outcomes for multiple myeloma patients.

B-cell maturation antigen is expressed on plasma cells. In this study, we have identified serum B-cell maturation antigen as a novel biomarker that can monitor and predict outcomes for multiple myeloma patients. Compared to healthy donors, patients with multiple myeloma showed elevated serum B-cell maturation antigen levels (P<0.0001). Serum B-cell maturation antigen levels correlated with the proportion of plasma cells in bone marrow biopsies (Spearman's rho = 0.710; P<0.001), clinical status (complete response vs partial response, P=0.0374; complete response vs progressive disease, P<0.0001), and tracked with changes in M-protein levels. Among patients with non-secretory disease, serum B-cell maturation antigen levels correlated with bone marrow plasma cell levels and findings from positron emission tomography scans. Kaplan-Meier analysis demonstrated that serum B-cell maturation antigen levels above the median levels were predictive of a shorter progression-free survival (P=0.0006) and overall survival (P=0.0108) among multiple myeloma patients (n=243). Specifically, patients with serum B-cell maturation antigen levels above the median level at the time of starting front-line (P=0.0043) or a new salvage therapy (P=0.0044) were found to have shorter progression-free survival. Importantly, serum B-cell maturation antigen levels did not show any dependence on renal function and maintained independent significance when tested against other known prognostic markers for multiple myeloma such as age, serum ß2 microglobulin, hemoglobin, and bone disease. These data identify serum B-cell maturation antigen as a new biomarker to manage multiple myeloma patients.

Soluble B-Cell Maturation Antigen Mediates Tumor-Induced Immune Deficiency in Multiple Myeloma.

PURPOSE: Reduced uninvolved immunoglobulin (Ig) levels are a hallmark of multiple myeloma. We previously showed that B-cell maturation antigen (BCMA) is solubilized and at high levels in multiple myeloma patient serum. We hypothesize that soluble BCMA binds B-cell-activating factor (BAFF) preventing its function to stimulate late B cells, and would result in lower polyclonal antibody levels in these patients. EXPERIMENTAL DESIGN: Mice were dosed with recombinant human BCMA (rhBCMA) and BCMA-BAFF complexes were analyzed in plasma, and its effects on antibody and Ig heavy chain mRNA levels determined. Using flow cytometry, BAFF binding to B cells was examined in the presence of rhBCMA and sera from multiple myeloma patients. In multiple myeloma sera, BCMA-BAFF complex formation and BCMA, IgA, IgG levels, and heavy-light chain isoform pair levels were determined. RESULTS: rhBCMA-BAFF complexes formed in immune-competent and deficient mice. Mice with human multiple myeloma xenografts, which contain plasma hBCMA and hBCMA-BAFF complexes, showed reduced plasma-free BAFF levels. rhBCMA administered to immune competent mice markedly reduced plasma IgA, IgG, and IgM levels and splenic Ig heavy chain mRNA levels. In serum from multiple myeloma patients, BCMA-BAFF complexes were detected and BAFF levels were reduced. Multiple myeloma patient sera containing BCMA prevented binding of BAFF to B cells. There is an inverse correlation between serum BCMA and uninvolved polyclonal Ig level in multiple myeloma patients. CONCLUSIONS: Our results show that soluble BCMA sequesters circulating BAFF, thereby preventing it from performing its signaling to stimulate normal B-cell and plasma cell development, resulting in reduced polyclonal antibody levels in multiple myeloma patients. Clin Cancer Res; 22(13); 3383-97. ©2016 AACR.

Serum B-cell maturation antigen is elevated in multiple myeloma and correlates with disease status and survival.

Although TNFRSF17 (also designated as B-cell maturation antigen (BCMA)) is expressed on tumour cells in B-cell malignancies, it has not been found in serum. The present study found that BCMA concentrations were higher in the supernatants of cultured bone marrow mononuclear cells from multiple myeloma (MM) patients than in healthy subjects. Serum BCMA levels were measured in samples from MM patients (n = 209), monoclonal gammopathy of undetermined significance (MGUS) individuals (n = 23) and age-matched controls (n = 40). BCMA was detected in the serum of untreated MM patients (n = 50) and levels were higher than in MGUS patients (P = 0·0157) and healthy subjects (P < 0·0001). Serum BCMA levels were higher among patients with progressive disease (n = 80) compared to those with responsive disease (n = 79; P = 0·0038). Among all MM patients, overall survival was shorter among patients whose serum BCMA levels were above the median (P = 0·001). We also demonstrated that sera from mice with human MM xenografts contained human BCMA, and levels correlated with the change in tumour volume in response to melphalan or cyclophosphamide with bortezomib. These results suggest that serum BCMA levels may be a new biomarker for monitoring disease status and overall survival of MM patients.

A novel angiogenesis model for screening anti-angiogenic compounds: the chorioallantoic membrane/feather bud assay.

Enhanced angiogenesis is a hallmark of solid tumors and hematological malignancies. Anti-angiogenic therapeutic approaches have recently been shown to be effective for the treatment of certain cancers. Endothelial cells migrating to tumors provide them with new blood vessels that are critical for their growth and survival. We have developed a novel and rapid method to evaluate the anti-angiogenic activity of new agents consisting of a combined chorioallantoic membrane (CAM) and feather bud (FB) assay. Unlike previous assays, this new assay assesses the effects of drugs on the ability of tissues to attract and develop their own blood supply. The CAM already has a well-developed vascular network that is capable of providing blood vessels to the non-vascularized FB, allowing for this tissue to develop feathers. As a result, the exposure of the FB to drugs for 2 days followed by attachment to the CAM for 4 days allows evaluation of the compound's ability to impact blood vessel and feather formation within the CAM-attached FB tissue. Feather formation is determined as well as expression of endothelial cell genes and proteins analyzed. Using agents with known anti-angiogenic activity including fumagillin, minocycline, zoledronic acid, doxorubicin and agents lacking anti-angiogenic activity such as melphalan, we have shown that the CAM/FB assay can accurately and rapidly assess the ability of agents to prevent blood vessel and feather development within non-vascularized tissues.

Pleiotrophin produced by multiple myeloma induces transdifferentiation of monocytes into vascular endothelial cells: a novel mechanism of tumor-induced vasculogenesis.

Enhanced angiogenesis is a hallmark of cancer. Pleiotrophin (PTN) is an angiogenic factor that is produced by many different human cancers and stimulates tumor blood vessel formation when it is expressed in malignant cancer cells. Recent studies show that monocytes may give rise to vascular endothelium. In these studies, we show that PTN combined with macrophage colony-stimulating factor (M-CSF) induces expression of vascular endothelial cell (VEC) genes and proteins in human monocyte cell lines and monocytes from human peripheral blood (PB). Monocytes induce VEC gene expression and develop tube-like structures when they are exposed to serum or cultured with bone marrow (BM) from patients with multiple myeloma (MM) that express PTN, effects specifically blocked with antiPTN antibodies. When coinjected with human MM cells into severe combined immunodeficient (SCID) mice, green fluorescent protein (GFP)-marked human monocytes were found incorporated into tumor blood vessels and expressed human VEC protein markers and genes that were blocked by anti-PTN antibody. Our results suggest that vasculogenesis in human MM may develop from tumoral production of PTN, which orchestrates the transdifferentiation of monocytes into VECs.

Pleiotrophin is highly expressed by myeloma cells and promotes myeloma tumor growth.

Pleiotrophin (PTN) is an important developmental cytokine that is highly expressed during embryogenesis but shows very limited expression in adult tissues, where it is largely restricted to the brain. High PTN serum levels are associated with a variety of solid tumors. We recently showed that patients with multiple myeloma (MM) also have elevated serum levels of this protein and the amount of PTN correlated with the patients' disease status and response to treatment. In this study, we demonstrate that MM cell lines and the malignant cells from MM patients' bone marrow produced PTN and secreted PTN protein into the supernatants during short-term culture. Moreover, Ptn gene expression correlated with the patients' disease status. Inhibition of PTN with a polyclonal anti-PTN antibody reduced growth and enhanced apoptosis of MM cell lines and freshly isolated bone marrow tumor cells from MM patients in vitro. Importantly, this antibody also markedly suppressed the growth of MM in vivo using a severe combined immunodeficiency (SCID)-hu murine model. This represents the first study showing the importance of PTN in the growth of any hematological disorder. Because the expression of this protein is very limited in normal adult tissues, PTN may represent a new target for the treatment of MM.